Chap. YI.] triciiinopoly district — ootatoor group. 103 



by great longitudinal (N. E. and S. W.) faults (of which I have nowhere 

 discovered the slightest indication,) would preserve a general paral- 

 lelism to the boundary, at all events as regards the higher beds which 

 could not be much affected by irregularities of the gneiss sea bottom. 



But this, as we have seen in the foregoing de- 

 Proof of unequal depo- 

 sition derived from di- scription, IS by no means the case. A glance at 

 vergent strike of bedding. .,, , , i -i t^ ^ 



the maps will show, e. g., that the strike oi tne 



highest beds seen may be followed from Garoodamangalum, where the 

 entire out-crop of the group is only a little more than 2 miles wide to 

 near Ilpagoody, where it has increased to more than 5 miles, and this 

 in a distance of 7 miles, while the average dip of the beds remains 

 almost unchanged, and indeed that of the higher beds is highest 

 where most distant from the boundary. Again, further to the North, 

 the out-crop of the group contracts rapidly, while the overlap of the 

 upper beds is very small, so that in a distance of 8 miles from the 

 line of widest extension beds, which at the latter point are between 

 4 and 5 miles from the boundary, approach to within 1 mile of it, 

 the average dip remaining, as before, unaltered. Now supposing 

 the beds to have been originally horizontal, and their inclination 

 due to unequal elevation, and taking the average dip throughout at 8°, 

 we should have a thickness in round numbers of 730 feet only at Garoo- 

 damungalum, and at Ilpagoody a thickness of not less than 1,900 feet 

 or an increase of 1,150 feet in 7 miles ; and again, in a further distance 

 of 8 miles this thickness would have diminished to rather less than 400 

 feet, a degree of variability which cannot be admitted in a horizontal 

 formation of such thickness. 



If, on the other hand, we suppose that the inclination of the bed- 

 ding is that of original deposition, the phenomena 



Phenomena best ex- . ^ i • j t, xi, -i.- x-l j. ^i. 



plained by the hypothesis are Simply explained by the supposition that the 



a se men a . deposits are those of a great bank stretching along 



the old Cretaceous shore, and that between Ootatoor and Maravuttoor, 



